Neurologic symptoms and signs in patients with sciatica were prospectively studied and compared with myelographic and operative findings in 403 cases with lumbar disc herniation as the cause of sciatica with special reference to accuracy of the clinical level diagnosis. Fifty-six percent of the herniations at L4-5. However, pain projection into the first sacral distribution was most common. Neurologic symptoms and signs of involvement of a single root were present in 239 cases and of two roots in 154 cases in L4-5 and L5S1 herniations. Pain projection into the fifth lumbar distribution was a very important symptom for identification of clinical findings of the fifth lumbar root involvement gave a level diagnostic accuracy comparable with myelography, while pain projection into the first sacral distribution was less reliable especially in cases with signs of two roots. The neurologic picture of high herniations was completely unreliable. Lumbar myelography or computer tomography is recommended as a routine preoperative study.